function animate(obj, target, callback) {
	clearInterval(obj.timer);
	obj.timer = setInterval(function() {
		var step = (target - obj.position().left) / 10;
		step = step > 0 ? Math.ceil(step) : Math.floor(step);
		if (obj.position().left == target) {
			clearInterval(obj.timer);
			callback && callback();
		}
		obj.css('left', obj.position().left+step + 'px');
	}, 15);
}
